La cuerda dulce – a tolerability and acceptability study of a novel approach to specimen collection for diagnosis of paediatric pulmonary tuberculosis

Abstract

BackgroundRecent data demonstrate the utility of the string test for the diagnosis of sputum-scarce HIV-associated TB in adults. We hypothesized that, if well-tolerated by children, this simple tool might offer a breakthrough in paediatric TB diagnosis. Thus the objective of this study, undertaken in the paediatric service of the Hospital Nacional Dos de Mayo, Lima, Perú, was to determine the tolerability and acceptability of the string test to paediatric TB suspects, their parents and nursing staff.Methods22 paediatric subjects aged 3–14 years (median 8) under investigation for TB were invited to undergo 2 string tests (four-hour downtime each). Subjective and objective pain and discomfort rating scales were used to assess the perception of the subject, parent and attending nurse.ResultsPatients as young as 4 years tolerated the procedure extremely well with 84% willing to undergo a second procedure. Peak discomfort at the time of swallowing and of string retrieval was mild (30% of maximum possible score) and brief as judged by visual analogue ratings and objective indicators. Good concordance of parent/child and objective/subjective ratings strengthened the validity of these findings.ConclusionThe string test is well tolerated and achievable for most paediatric TB suspects as young as 4 years. A formal prospective paediatric efficacy study is now needed.

Intra-gastric string test: an effective tool for diagnosing tuberculosis in adults unable to produce sputum

“…However, the device is extremely simple and could easily be produced locally, as shown by Peru, which developed string capsules made in-house for ,$0.20 each using market-purchased gelatine capsules. 19 In addition, it has a reduced risk of TB transmission compared to sputum induction, which is particularly important in patients with presumption of drug-resistant tuberculosis. These advantages for health care workers can also be obtained when using nasogastric aspiration; however, the tolerability and feasibility of nasogastric aspiration in out-patient settings might be lower than with the string test.…”

“…Discomfort was rated by the patient at various time points using a visual analogue scale of 0 to 10 (0 ¼ no discomfort and 10 ¼ worst possible discomfort) 19,20 (Appendix). * Any adverse events were recorded.…”

Xpert<SUP>®</SUP> MTB/RIF for detection of <I>Mycobacterium tuberculosis</I> from frozen string and induced sputum sediments

“…1,2 TB incidence and prevalence are likely to be underestimated due to the difficulty in obtaining samples among non-expectorating patients, 3 especially children, severely ill adults and patients co-infected with the human immunodeficiency virus (HIV). 4,5 A number of less invasive but well-tolerated alternative approaches have recently been developed to improve sample collection for TB diagnosis among non-expectorating patients; these include the 'la cuerda dulce' (sweet string) 6 method and induced sputum. The string test (ST) consists of a coiled nylon string inside a weighted gel capsule.…”

“…The string test (ST) consists of a coiled nylon string inside a weighted gel capsule. 6 After being swallowed by a patient, the string unravels through a hole at the weighted end of the capsule as it descends into the stomach and the capsule dissolves. The string becomes coated with gastrointestinal secretions containing any pathogens present in the stomach.…”

“…After retrieving the string by gently pulling, it is placed in 0.9% saline solution. 6 Induced sputum (IS) is another method of obtaining samples for TB evaluation from non-expectorating patients. Sputum induction involves the administration of an inhaled bronchodilator and nebulised hypertonic 3-5% saline, followed by the nasopharyngeal aspiration or expectoration of mucus from the lower respiratory tract.…”